Patients receive radiation treatments Monday through Friday and injections of PS-341 twice a week during the radiation therapy. After 3 weeks of treatment, PS-341 injections are stopped for 2 weeks. Some patients continue to receive radiation treatments during the 2-week break, and others do not, depending upon when they enter the trial. The total duration of radiation treatment varies from 6 to 8 weeks, depending on whether the patient received radiation in the region of the head and neck cancer before entering the study.